Web dryer

ABSTRACT

A dryer for webs having freshly applied printed designs and coatings is disclosed. The dryer has an involute conduit formed of a plurality of runs disposed angularly with respect one to the others. The web is drawn through the conduit and exits from the conduit into a central cavity in which is disposed a receiving element for receiving the then dry web. Heated air is introduced into the conduit for drying the web and carrying off the volatile constitutents of the material applied to the web. When the receiving element is a take-up reel, a leader greater in length than the conduit is used to draw the leading edge of the web through the dryer. A photocell sensor determines the presence of a portion of the web to be dried and causes the take-up reel to be driven to draw the web through the dryer.

United States Patent 11 1 Loser 1 1 Aug. 7, 1973 WEB DRYER [76] Inventor: Alois Loser, R.D. No. 1, Box 29, f Domy M edford NJ 08055 Assistant Examiner-Larry l. Schwartz Attorney-Synnestvedt & Lechner [22] Filed: Oct. 26, 1971 21 Appl. No.: 192,155 [57] ABSTRACT A dryer for webs having freshly applied printed designs and coatings is disclosed. The dryer has an involute 52 us. Cl. 34/56, 34/155 conduit formed on plurality ofmns disposad angularly [51] Illt. Cl. F26) 13/10 i respect one to the others. The web i drawn [58v] Fleld of=Search 34/56, 152, 153, a through the conduit and exits from the conduit into a 34/155 160 central cavity in which is disposed a receiving element for receiving the then dry web. Heated air is introduced [56] References C'ted into the conduit for drying the web and carrying off the UNITED STATES PATENTS volatile constitutents of the material applied to the 703,044 6/1902 Crowell 34/155 w h h receiving l m is ta p reel. 1 1,992,989 3/1935 Burns 34/155 leader greater in length than the conduit is used to draw 772,695 10/ 90 Crowell r r 34/155 the leading edge of the web through the dryer. A photo- L432-3O2 10/1922 Reed 34/155 cell sensor determines the presence of'a portion of the 3 g 12 web to be dried and causes the take-up reel to be driven 2:624:573 11953 iii 2 .18 draw the web thmugh h 3,239,948 3/1966 Di Mino 34/161 5 Claims, 6 Drawing Figures PATENIEW 3.750.305

sum 2 OF 3 FIG. 11o

INVEN TOR ALOIS LOSER PATENTED AUG 3. 750. 305

SHEET 3 OF 3 INVENTOR ALOIS LOSER WEB DRYER BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to drying apparatus for webs which have had a design or coating of a settable material applied to one side thereof. More particularly, this invention relates to web dryers of the type in which the web is drawn in an involute path through the dryer, during which the web is exposed to a conditioned gaseous stream which dries the web and carries off the volatile constituents of the applied material. Drying apparatus of the type here described is particularly adapted for use with batch-type printing operations such as manual and'semimanual silk screening.

2. Description of the Prior Art In the production of such materials as wallpaper or the like where the pattern is multicolored, in almost all instances, the finished designs are formed by the serial application of each of the colors of the pattern to the web. That is, first one color of the design is applied to the entire web and then the succeeding colors of the design areapplied in a like manner. It is also common to apply "designs to the web in a discontinuous manner, leaving the width-of at least one design between each discreet application of material to the web. The pattern is applied irf thisfmanner to avoid smudging of the edges of adjacent portions of the newly applied pattern by contact'witli the printing mechanism.

Between-succeeding color application steps, it is nec- 'e'ssa'ryto dry the 'web thoroughly so that the previously applied coloring material-is not smudged or otherwise defaced whentheweb is handled prior to or during the next color application step.

One way in whichwebs are dried is to hang or drape theweb in racks to expose the wetted web freely to the ambient air to promote drying. This procedure requires the expenditure "of labor costs to position the webs on the racksand also requires a large amount of floor space to be devoted to the drying area.

In order to obviate the disadvantages 'of the drying rack discussed above, it has been known to use web dryers that draw the web inwardly in an involuted path and which, during the transport of the web through the dryer, subject the web to conditioned air. These known prior art designs are of the cabinet type wherein the web is caused to move through the dryer over an involute array of driven rolls mounted in a surrounding cab SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a new and improved dryer for drying webs, which dryer is compatible with batch-type printing operations, less costly to purchase and maintain, has improved drying efficiency, is compact, and which can be constructed in accordance with uncomplicated sheet metal techniques.

Briefly, these and other objects of this invention are achieved by a dryer design incorporating a closed, generally air-impervious conduit comprised of a plurality of duct sections. The duct sections are arranged so that the web in its transport through the dryer follows an involute path. The conduit is provided with a device for effecting the drying of the web as it passes through the conduit. The dried portion of the web is received upon an element mounted in the interior of the involute path for storing or redirecting the dried portion of the web.

DESCRIPTION OF THE DRAWINGS FIG. I is a side elevation of the preferred form of drying apparatus.

FIG. Ila isa schematic illustration showing the start of the web take-up sequence.

FIG. IIb is a schematic illustration of the web take-up sequence showing the position of the web loop when the take'up drive is de-energized.

FIG. is a schematic illustration showing the dried web being returned to the supply roll 26.

FIG. III shows a second dryer embodiment having a hexagonal web path.

FIG. IV illustrates a typical take-up reel drive mechanism.

Referring now to FIG. I, which shows the preferred embodiment of the invention of dryer 1, the dryer is composed of an involute conduit 2. The consuit 2 is formed from duct sections 2a, 2b, 2c and 2d, joined in a manner to be hereinafter discussed. The duct sections 2a, 2b, 2c and 2d are of rectangular cross section, as it is ducts of this cross section which are most easily fabricated.

In'the preferred embodiment, a first run of the conduit 2 is formed by a straight horizontal duct section 20. One end of the cut section 2a is received in a joining member 200 which is generally in the nature of an elbow section. A second run is formed by straight duct section 2b which is received at one end in joining member 20a and at the other end in apex joining member 21. As shown in FIG. I, the duct-section 2b extends downwardly from and beneath duct section 2a. A third run is formed by straight duct section 2c which at one end is received in apex joining means 21. Duct section 2c extends upwardly and at its other end is received in joining means or elbow 20b. A fourth run is formed by straight horizontal duct section 2d which atone end is received in the joining member 20b. The other end of duct section 2d terminates at exit opening 12 spaced from the joining means 20a and duct section 2b, as shown in FIG. I.

Thus, it can be seen that an involute passageway of generally triangular configuration is formed for the passage of web 10 therethrough. The duct sections 2a, 2b, 2c and 2d all include relatively flat, smooth supporting surfaces, such as surfaces 7, 7 and 9, 9' over which the web is transported. Further, the joints between the duct sections 20, 2b, 2c and 2d and the joining members 20a, 20b and 21 are smooth and otherwise free of edges or surfaces which would snag or abrade the web. These joints are generally fluidtight so that a stream of gas may be caused to course through the conduit for reasons to be herein later described. Joints having these attributes are known conventionally to those knowledgeable in the art of sheet metal fabrication andno detailed disclosure of these is necessary.

As can also be readily seen from FIG. I, the above described assembly defines in its central portion a large cavity 13. Within this cavity 13 can be mounted elements necessary for the conditioning and handling of the web as will be later described.

At each point of direction change of the web in the dryer is placed a flanged roller to assist in such direction changes. Entrance roller 6 is placed adjacent the entrance 3 to the first run of the dryer formed by duct section 2a. Rollers 8a, 8b and 8c are contained in the joining members 20a, 21 and 20b respectively. Exit roller 14 is mounted adjacent the exit opening 12 of the fourth run of the dryer formed by duct section 2d. The rollers 6, 8a, 8b, 8c and 14 are all freely rotatable.

Above the entrance 3 to the first run formed by duct section 20 is an induction unit for introducing a drying gas, such as heated air, into the conduit 2. The induction unit 4 can be comprised of a conventional squirrel cage-type and housing, the outlet of which directs air onto the heating elements of an electrical resistancetype heater, designated as 4a, and thence into the conduit 2. The induction unit 4 may include in its control circuit (not shown) a thermostat for maintain the drying air at a desired temperature and suitable safeguards to prevent the energization of the heater 40 before an adequate volume of air is supplied by the fan motor. Another source of heat energy may be a plurality of infrared lamps mounted in the conduit. While the induction unit has been shown positioned at the upstream end of the conduit 2, thereby creating a current of drying gas which moves in the direction of travel of the web 10, such an induction unit could equally well be placed at the downstream end of the conduit at opening 12, thereby creating a flow of drying gas which is counter to the direction of travel of the web. Further, it is equally within the scope of a disclosed preferred embodiment to mount an exhaust unit at either end of the conduit to assist in or cause a flow of drying gas within the conduit. A baffle is disposed in the entrace 3. Baffle 5 is placed adjacent the entrance opening 3 to minimize the escape of drying gas therefrom.

Mounted on each side of the dryer on the ducts 2b and 2c is a horizontal support member, such as member 16. Disposed between the support member 16 is a webreceiving element.

For purposes of the invention, the web-receiving element can be a flanged take-up reel 15, as shown, or an obliquely disposed turning bar or roller or similar element which directs the dried portion of the web laterally outward of the cavity 13. In the case where the web-receiving member is a take-up reel, a suitable drive means 17 is provided for driving the take-up reel. This drive means includes a motor, a gear reduction unit, and an electrically actuated magnetic clutch 17 disposed between the gear reduction unit and the takeup reel. The drive means 17 is mounted exteriorly of the cavity 13 on one of the members 16. The drive system for driving take-up reel also includes drive pulley 30 mounted on the output shaft of clutch 17'. Drive pulley 30 drives pulley 34 via belt 36. The pulley 34 is fixedly mounted to an extension of the axial shaft of take-up reel 15. The take-up reel 15 is journally mounted at each end to members 16 by bearings, such as bearing 38.

Pairs of support elements 18a and 18b are disposed on opposite sides of the dryer to support the dryer in upright condition. These support members 18a and 18b can be constructed of angle stock and are secured to the conduit 2 by tack welding or bolts.

FIGS. Ila, llb and llc show the dryer 1 in the contemplated operating environment. The environment includes a printing table 23 which forms the supporting surface for the web 10 as it is undergoing a printing or coating operation. At one end of the table 23 is a supply reel 26 on which the web 10 is stored prior to the printing or coating operation. The element designated 27 schematically illustrates a silk screen frame or similar printing element which is capable of being moved veritcally into and out of engagement with the upper surface of the web.

Placed on a leg of the table 23 or adjacent the end of the table 23 is a light source 24 disposed above the floor F. Mounted to the dryer 1 is a photocell 25 which is positioned the same distance above the floor F as light source 24 and which is aligned therewith so that the beam from light source 24 will impinge on photocell 25. The light source 24 and photocell 25 are of a type which is commonly commercially available and no additional description is believed necessary other than that the photocell is of a conventional type, i.e., one that changes its electrical properties, such as the resistance, in response to the impingement of light thereon. Photocell 25 forms the control element of the circuit (not shown) energizing the magnetic clutch 17' of the drive means 17. Lines L, and L, schematically represent the conductors connecting photocell 25 to magnetic clutch 17. The photocell 25 and its accompanying circuitry are of a type which is commonly commerically available and the details thereof form no part of the invention herein disclosed. It sufiices to describe the circuit in terms of its operation as follows: when there is no light from source 24 impinging on photocell 25, the magnetic clutch of drive means 17 is actuated, causing the take-up reel 15 to be rotated. Conversely, when light falls upon the photocell 25, the clutch 17' is deactivated.

Alternatively, the element 17 can be a combined magnetic clutch and brake unit. Such a unit operates in the same manner as described above except that when light impinges on photocell 25, the clutch portion of the unit is deactivated and the brake portion is actuated. The output shaft of the unit 17' is prevented from rotating and, therefore, the movement of the reel 15 and is drive system comprised of pulleys 30 and 34 and belt 36 is prevented. This arrangement eliminates the tendency of the take-up reel 15 to backwind when the drive system is idle and serves to keep the portion of the web 10 in the dryer taut.

As shown in FIG. lla, dryer 1 also includes a carrier or leader element 22. Element 22 is comprised of any strong flexible web of material, such as canvas or nylon, and is attached to one end to the spindle of take-up reel 15. The length of the leader 22 is somewhat greater than the length of conduit 2 so that the free end of the leader can be drawn through the conduit to extend beyond the entrance opening 3. To this free end of the leader 22 is secured the leading edge of the web 10. This securing can be accomplished by one of many known methods, for instance, by sewing or taping the leading edge of web 10 to free end of the leader 22. Leader 22 is provided so that at start-up the web can be drawn into the dryer without the need for manually threading the web through the dryer.

Mounted within the cavity 13 is a source of cool air such as cooling fan 19. The stream of cool air issuing from fan 19 is directed toward take-up reel 15. The

purpose of this stream of cold air is to give a final set to the material printed on the web to lessen the likelihood that the printed matter will be marred as succeeding convolutions of the web are wound on the take-up reel. r

While in the description of the preferred embodiment above, the conduit 2 has been described as having a generally triangular configuration, it is considered to be-within the scope of the invention to utilize other similar involute configurations. For example, in FIG. III is shown another embodiment with a conduit having a hexagonal configuration, the conduit being formed of six straight duct sections 32a, 32b, 32c, 32d, 32e, 32f and 32g. It will be noted that this configuration also includes large central cavity 13' in which can be mounted a web-receiving member such as take-up reel 15.

The operation of the dryer will next be described in connection with a typical printing or coating operation which the web undergoes prior to the time that it is dried.

At start-up, the web is contained on supply reel 26. The leading edge of the web is drawn across the table 23' and is attached to the end of leader 22. The frame 27 is brought into engagement with the upper surface of-web 1t) and the printing operation is completed. The frame 27 is then raised and the operator manually pushes the web across the surface of table 23 to position a new section web beneath the printing frame 27.

When the web reaches the edge of the table 23, it falls therefrom to form loop 100 between the edge of the table and the entrance to the dryer. The loop 100 of the web 10 interrupts the passage of light from light source 24 to photocell 25, thereby changing the electrical characteristic of the photocell 25 and causing the actuation-of the magnetic clutch 17 upon actuation of as shown in the drawing, thereby causing causes a"port1onof the web forming loop 10a to be drawn into the dryer.

When thefl'b'ott'om of the loop 10a reaches a point above thelight' source 24' and cell 25, as shown in FIG. llb, the magnetic clutch is deactuated and movement of the web through the dryer ceases. When the operator of the frame 27 has completed the printing operation and again advances the web across the table to form a large loop lltla, as in FIG. Ila, the cycle is repeated.

FIG. Ilc shows the rewinding of the web onto supply reel 26 in preparation for an additional printing operation. At this time, the loop 100 either becomes very small or ceases to exist so that the web is spaced well above the light source 24 and photocell 25, thereby precluding actuation of the clutch 17'. With the clutch 117 disengaged, the reel 15 is free to rotate in a counterclockwise direction as the web 110 is drawn off the reel.

It should be noted that the single most important de sign criteria for dryers of the type disclosed is that the side of the web which receives the applied pattern must not come into contact with any portion of the dryer until the material applied has been fully dried and set. In order to achieve this result, it is necessary to maintain the web end closely adjacent the flat surfaces 7, 7 and 9, 9. This problem becomes especially critical when considered in the light of the operating environment heretofore described which, as will be remembered, is in many instances a batch-type operation. The

vance through the dryer. This in turn probiem arises partly from the use of ducts having-small cross-sectional heights. From a study of FIG. I, it can be seen that the web, if untensioned, is sufficiently heavy, either by reason of the weight of the web itself, the weight of the material applied, or both acting in conjunction, that on the second and third runs through ducts 2b and 2c, the web 10 might hang in catenary fashion from the rollers 8a and 8b or 8b and 80, thereby causing wet portions of the web 10 to come into contact with the interior surfaces of the duct, causing a smearing of the pattern to take place.

Of couse, one solution to this'problem would be to tension the web. However, there are two factors militating against this solution. One is that the web in wetted form is capable of sustaining only very limited stress in tension. The other is that known mechanical tensioning schemes add cost and maintenance problems to the dryer unit.

Another solution to this problem would be to increase the cross-sectional height of the ducts. However, this would add to the material costs of fabricating the conduit, would require the use of air-handling equipment of greater capacity and, therefore, greater expense, and would reduce the overall compactness of the dryer.

The preferred embodiment of the disclosed invention solves the problem of web contact with the duets without the need for increasing cross-sectional height thereof by a combination of features. The first consideration is that in the first'run, the web is supported in a flat, horizontal position with its contact-sensitive surfaces free from engagement with inner surfaces of the duct. The second consideration is that in those runs where the contact-sensitive of the web is most likely to come in contact with the interior of the duct, namely the second and third runs forms by ducts 2b and 2c, the ducts are inclined with respect to the horizontal plane. This minimizes the distance by which the web 10 falls away from surfaces 9 and 9'. As previously stated, this allowsthe use of ducts of lesser cross-sectional height.

It should also be noted that because the web stays in close proximity to the surfaces 9 and 9', the continuous stream of air passing through the conduit tends to urge the web against these surfaces. Further, it shall also be realized that the material feed-control system also aids in this regard. The loop which is maintained at all times immediately adjacent the dryer entrance causes, by reason of its weight, a slight back tension which tends to, but does not, draw the web out of the dryer. This back tension in turn causes the web 10 to be held more closely against the surfaces 7, 7' and 9, 9' during the period when the take-up reel is stationary.

One other manner of causing the web to be placed under light tension is to place a vacuum hold-down device, such as element 28, at the entrance to the dryer. This may consist most simply of a plenum maintained under vacuum and in communication with an apertured plate. Such a device will cause the web to be pulled down upon the apertured plate and would create a drag on the web, thereby reducing the amount of slack of the web position in the dryer. This will tend to hold the web closer to the surfaces 7, 7' and 9, 9' and out of contact with parts of the dryer capable of defacing the web. Tensioning the web in this manner will also lessen the lateral shifting of the web within the duct 2 which causes the edges of the web to contact interior surfaces of the duct, causing damage to such edges.

An additional advantage arises from the fact that the first run is horizontally disposed. It must be remembered that the web is weakest in its wetted condition. The preferred embodiment lessens the likeihood that the web will be tore while in this condition by reason of the fact that the first run is horizontal and therefore the web is supported on the flat surface throughout this entire first run.

In addition, the ducts forming the runs of the conduit in the preferred dryer embodiment have been illustrated as being straight ducts of rectangular cross section. It should be realized that this duct configuration is one that is most easily and inexpensively fabricated and one which yields other advantages in terms of web support and ease of machine maintenance. It is within the scope of the present invention to employ duct cross sections other than that shown."

Finally, it should be realized that the primary comtemplated environment of the disclosed dryer is that of small volume and batch-type printing operations, such as silk screening. The features disclosed, such as the triangular involute conduit and the photocell control system allow the use of inexpensive air supplying and takeup roll driving equipment. It is these features that yield an inexpensive automatic dryer construction which can be used successfully with low volume batch-type printing operations. These features allow the contactsensitive web to be passed through the dryer without defacement and consequent waste. However, it should be realized that the dryer disclosed, when operated in a continuous manner, has high speed drying capabilities. It is, therefore, also compatible for use with high volume production processes.

I claim:

1. Apparatus for drying a web having a wetted surface comprising a conduit formed of first, second and third substantially straight runs, the longitudinal axis of th'e runs arranged in a triangular array, the first run being generally horizontally disposed and including a web entrance, the second run extending angularly downwardly beneath the first run and the third run extending angularly upwardly from the end of the second run toward the first run, the angles of the longitudinal axis of each of the second and third runs with respect to a horizontal plane being such that the web is sup ported with the wetted surface thereof free from contact with the interior surfaces of the conduit as the web travels through the conduit, joining means for joining the first run to the second run and joining means for joining the second run to the third run, the intersection of the second run and third run being beneath the first run, a cavity formed within the triangular array of runs, receiving means mounted within the cavity for receiving the web, and means for introducing a drying gas into the conduit.

2. Apparatus according to claim 1 wherein the conduit includes a fourth run disposed beneath the first run and generally parallel thereto.

3. Apparatus for drying a web comprising, a closed involute conduit having a surface therein for supporting a web with one surface thereof free from contact with the interior surfaces of the conduit, the conduit having at least one vertical direction change therein; a cavity defined by the conduit; means for effecting drying of the web; and a reel disposed in the cavity for receiving a dried portion of the web; and a leader of a length greater than the length of the conduit attached to the reel.

4. Apparatus for drying a web comprising, a closed involute conduit having a surface therein for supporting a web with one surface thereof free from contact with the interior surfaces of the conduit, the conduit having at least one vertical direction change therein; a cavity defined by the conduit; means for effecting drying of the web; a reel disposed within the cavity; drive means for driving the reel; and control means responsive to the presence of portions of the web to be dried for actuating the drive means.

5. Apparatus according to claim 4 wherein the closed conduit includes a first substantially horizontal run having entry means at one end thereof for providing entry of the web into the conduit, and wherein the control means includes a photocell detector means position to detect the presence of portions of the web disposed below the entry means.

V UNITED sTATEs PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,750,305 Dated August 7, 973

Inventor(s) AlOis Loser It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line '53, "to" should read -at-*-.

Column 6, line 34, insert --surfaceafter "contactsensitive", I

Column 7, line 5, "tore"should be read --torn--'.

Signed and sealed this 30th day of July 1971,.

Attest:

MCCOY M. GIBSON, JR. 0. MARSHALL DANN Attesting Officer Commissioner of Patents FORM P0-1050 (10-69) uscoMM-Dc 60376-P69 U,S. GOVERNMENT PRINTING OFFICE: I969 0-356-334 

1. Apparatus for drying a web having a wetted surface comprising a conduit formed of first, second and third substantially straight runs, the longitudinal axis of the runs arranged in a triangular array, the first run being generally horizontally disposed and including a web entrance, the second run extending angularly downwardly beneath the first run and the third run extending angularly upwardly from the end of the second run toward the first run, the angles of the longitudinal axis of each of the second and third runs with respect to a horizontal plane being such that the web is supported with the wetted surface thereof free from contact with the interior surfaces of the conduit as the web travels through the conduit, joining means for joining the first run to the second run and joining means for joining the second run to the third run, the intersection of the second run and third run being beneath the first run, a cavity formed within the triangular array of runs, receiving means mounted within the cavity for receiving the web, and means for introducing a drying gas into the conduit.
 2. Apparatus according to claim 1 wherein the conduit includes a fourth run disposed beneath the first run and generally parallel thereto.
 3. Apparatus for drying a web comprising, a closed involute conduit having a surface therein for supporting a web with one surface thereof free from contact with the interior surfaces of the conduit, the conduit having at least one vertical direction change therein; a cavity defined by the conduit; means for effecting drying of the web; and a reel disposed in the cavity for receiving a dried portion of the web; and a leader of a length greater than the length of the conduit attached to the reel.
 4. Apparatus for drying a web comprising, a closed involute conduit having a surface therein for supporting a web with one surface thereof free from contact with the interior surfaces of the conduit, the conduit having at least one vertical direction change therein; a cavity defined by the conduit; means for effecting drying of the web; a reel disposed within the cavity; drive means for driving the reel; and control means responsive to the presence of portions of the web to be dried for actuating the drive means.
 5. Apparatus according to claim 4 wherein the closed conduit includes a first substantially horizontal run having entry means at one end thereof for providing entry of the web into the conduit, and wherein the control means includes a photocell detector means position to detect the presence of portions of the web disposed below the entry means. 